Linq返回指定类型

1.

public IEnumerable<RiskInfo> GetRisksByUsername()
{
AuroraDataContext db = new AuroraDataContext();
var list = db.GetRisksByUsername().Select(c => new RiskInfo { Number = c.Number, Name = c.Name });

return list;
}

public class RiskInfo
{
public int? Number { get; set; }
public string Name { get; set; }
}

2.

下面给出个简单的例子：

 

publicinterface IStockStatistics
    {
        IT_Modelnumber ModelNumber { get; set; }
        int TotalAmount { get; set ;}
    }

public class StockStatistics:IStockStatistics 
    {
        private int _id;
        private IT_Modelnumber  _model;
        private int _amount;

        public int Id
        {
            get{return _id  ;}
            set{_id =value ;}
        }
        public IT_Modelnumber ModelNumber
        {
            get { return _model; }
            set { _model = value; }
        }
        public int TotalAmount
        { 
            get { return _amount; }
            set { _amount = value; }
        }
    }

public ICollection<IStockStatistics > GetStatistics()
         {
              var result = from p in Database.StockDS
                           group p by p.ToModelnumber into g
                           select new StockStatistics
                           {
                               Id = g.Key.Id,
                               ModelNumber = g.Key,
                               TotalAmount = g.Sum(p => p.Amount)
                          };
             return result.AsEnumerable().Cast<IStockStatistics>().ToList().AsReadOnly();
         }

 简单的说这个方法就是将原本匿名的类型转换成我们已知的类型，但这个类型不存在，所以需要我们先进行定义。

select new StockStatistics :new 后面的类型有些资料中省略了，但我在自己的环境中省略后编译没有通过。